The present invention relates to a cathode ray tube (CRT) assembly of a projection TV system, and more particularly, to a CRT assembly of a projection TV system
All too often, in a CRT assembly for a TV projection system, a coupler which holds the coolant requires an oil cap and an oil cap holder for controlling the pressure of the coolant in the coupler in addition to a separate coolant injection hole for filling the coupler with coolant. Such an arrangement requires two seals and two separate entities for operation of the coupler which is costly, cumbersome, and difficult to manufacture. What is needed is a coupler which holds coolant and is connected to the CRT assembly that uses a single coolant injection hole for both filling the coupler with coolant and for controlling the pressure of the coolant in the coupler.
Referring to FIG. 1, a typical projection TV system is for projecting an image formed by a CRT assembly A installed inside a main body 1 to a rear surface of a screen 3 installed in the front side of the main body 1 by reflecting the image by a reflection mirror 2. FIGS. 2 and 3 are a sectional view and an exploded perspective view of a conventional CRT assembly, respectively. Referring to the drawings, the conventional CRT assembly includes a CRT 10 for forming an image, a coupler 20 coupled to the front surface of the CRT 10, and a projection lens 30 for magnifying and projecting the image formed at the CRT 10.
The CRT 10 and the projection lens 30 are coupled to the coupler 20 through sealing members 11 and 31 and fixing brackets 12 and 32. A coolant receiving portion 21 and a coolant injection hole 22 are formed at the coupler 20. The coolant receiving portion 21 is formed at the center of the coupler 20 and contains coolant C in inner space sealed by the CRT 10 and the projection lens 30. The coolant injection hole 22 is for injecting coolant C into the sealed space and is sealed by a bolt 23 coupled to the coolant injection hole 22 and a sealing member 24 to prevent leakage of coolant C. Also, the conventional CRT assembly includes a hole 25, an oil cap 26 and an oil cap holder 27 as a pressure control device, for controlling the pressure of coolant C contained in the coolant receiving portion 21 when the temperature of the CRT 10 increases.
The hole 25 is formed at one surface of the coupler 20 to penetrate the inside and outside of the coolant receiving portion 21. The oil cap 26 is dome shaped so that a part thereof can be inserted into the inside of the coolant receiving portion 21. The oil cap 26 is formed of a soft material such that, when the inserted part of the oil cap 26 contacts coolant C and the pressure of the coolant C increases, a convex portion of the oil cap 26 can be deformed to be concave and thus the pressure of coolant C can be absorbed in a direction in which the inner space of the coolant receiving portion 21 increases. The oil cap holder 27 is for fixing the oil cap 26 to the coupler 20 to prevent coolant C from leaking between the oil cap 26 and the hole 25.
However, in the conventional CRT assembly of a projection TV system, the coolant injection hole 22, the bolt 23 and the sealing member 24 are needed at the coupler 20 for injecting coolant C and the hole 25, the oil cap 26 and the oil cap holder 27 are needed for controlling the pressure of coolant C. Thus, as the structures for injecting coolant and for controlling the pressure of coolant are respectively needed, the number of parts increases and the assembly work becomes complicated. Also, in a state in which the oil cap 26 and the oil cap holder 27 are installed at the CRT assembly, the oil cap 26 continues to contact coolant C. Accordingly, when the pressure of coolant C increases excessively due to the heat of the CRT 10, the oil cap 26 is destroyed by the excessive pressure of coolant C and the coolant C leaks from the coupler 20.
To solve the above problems, it is an objective of the present invention to provide a CRT assembly of a projection TV system in which the structure for injecting coolant into the coolant receiving portion of the coupler and controlling the pressure of the coolant is improved.
It is also an object to provide a CRT cooling system that uses a single coolant injection hole to both fill the cooling system with coolant and to control the pressure of the coolant in the cooling system, thus avoiding the need for separate ports for filling the cooling system with coolant and controlling the pressure of the cooling system.
It is also an object to provide a coupler containing coolant for a CRT in a TV projection system that is easy to manufacture and requires fewer parts. Accordingly, to achieve the above objects there is provided a CRT assembly of a projection TV system which comprises a CRT for forming an image, a projection lens for magnifying and projecting the image formed by the CRT, a coupler installed between the CRT and the projection lens, a coolant receiving portion formed at the center of the coupler, having a front surface in contact with the projection lens forming a seal and a rear surface in contact with a front surface of the CRT forming a seal, a coolant injection hole formed to penetrate the side of the coolant receiving portion, through which coolant is filled in the coolant receiving portion, and a pressure control device for controlling the pressure of coolant in the coolant receiving portion while sealing the coolant injection hole.